I googled the model to see what type of card you have cause typically when pushing audio thru HDMI it gets run thru the video card
The result was your laptop has nvidia GPU inside, in which case the HDMI audio option should be in the geforce control panel
There could also be an option in bios but I'd check the geforce first
If I were to guess why the TV alone works, most newer TVs get auto detected under the windows system itself and given control by the system volume where as your other device is routing the sound or so it would seem maybe it is having trouble auto detecting
Since I understand what your trying to accomplish there is also a way if you haven't done so already to set the laptop to do nothing when the lid is closed and enable the monitor to shut off but not the hardrive
Then when playing music, watching a video or anything you could close the lid or let the monitor shut off without interrupting the media
CoolerMaster HAF 932 Advanced/ Maximus VI Formula/ I7-4770K/Swiftech H320/ Corsair HX850/ G.Skill Trident X (2x8) 16gb 2400MHz/ 2x 840 EVO 120gb(Raid 0)/ WD 1TB HDD (Backup/Storage)/ EVGA GTX 1gb 560 TI/ Asus 12x bluray combo